Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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BREAKER PLATES FOR SHAKING TABLES AND ROTARY DRUMS
BACKGROUND OF THE INVENTION
(i) Field of the Invention
This invention relates to apparatus for processing large cohesive lumps or
agglomerates of abrasive materials for size reduction and, more particularly,
relates to
breaker plates having protrusions with an abrasion, wear and impact resistant
coating for
size reduction and sieving in high wear applications typified by the mining of
oil sands or
coal.
Mining of oil sands involves excavation and transfer of huge volumes of
stratified
sand saturated with bitumen for recovery of hydrocarbons. The sand essentially
is a quartz
sand angular in shape and as a result very abrasive to steel equipment. The
hard facing of
steel equipment to resist wear and erosion by coating exposed steel surfaces
with tungsten
carbide particles dispersed in a matrix of mild steel or a nickel- or cobalt-
base alloy is
known. U.S. Patent No. 4,013,453 for example discloses hard surfacing of a
metal
substrate by coating with a nickel-base matrix powder mixed with coarse
tungsten carbide
particles to resist wear and abrasion. It is stated that such coatings are
sensitive to thermal
cracking and spalling due to the brittle nature of the coating.
The hard facing of equipment used for the mining and handling of oil sands is
particularly sensitive to wear, to erosion due to abrasion, and to spalling
due to the shock
of impact from dropping of large lumps of oil sand on shaker boxes or rotary
breaker
drums for wet screening the sands with water and for breaking oversized
cohesive lumps
down to a size suitable for passage as undersize through hole openings in the
shaker boxes
and rotary drums. U.S. Patent Application Serial No. 12/153,327, the contents
of which
are incorporated herein by reference, discloses hard facing a metal substrate
with a two-
layer abrasion and impact resistant coating by fusing a softer inner first
coat of a matrix
alloy of nickel-, cobalt- or iron-base alloy with carbide particles onto the
substrate and
fusing a harder second outer coat of a matrix alloy of nickel-, cobalt- or
iron-base alloy
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with angular carbide particles onto the softer inner first coat. The softer
inner first coat
preferably has a hardness of about 30 - 40 Rc and the harder outer second coat
preferably
has a hardness of about 50 - 60 Rc. The carbide particles preferably are
tungsten carbide
particles in the size range of about 60 to 250 and comprise about 55 to 65
wt% of each of
the inner and outer coats.
The large cohesive oversized lumps of oil sands feed material which are not
broken
down during the primary breaking and size reduction process tend to flow
through or
across the sieve structure of the sizing equipment necessitating recycling of
the material or
loss of valuable product, or causing excessive wear and impact damage to the
breaker
plates.
Summary of The Invention
It is a principal object of the present invention therefore to provide breaker
plates
for improved size reduction of oversized lumps of cohesive material typified
by oil sands
as the over size lumps are received from primary crushing.
In its broad aspect, the breaker plate of the invention comprises a
rectangular plate
with spaced-apart sidewalls and endwalls and equispaced rows of holes formed
in the plate
extending across the plate on a surface thereof from one side to the other,
and rows of
pyramid projections or wedge projections formed on the surface of the plate
between the
rows of holes and extending from one side of the plate to the other. One or a
plurality of
the pyramid projections or wedge projections are formed on base strips and the
base strips
attached by welding onto the surface of the plate. The pyramid projections or
wedge
projections may be attached to the surface of the plate out of alignment with
the holes or
the rows of the pyramid projections may be attached to the surface of the
plate with
alternate rows out of alignment with the holes. The pyramid projections or
wedge
projections preferably are hard surfaced with a dual layer hard faced coating
for impact
resistance.
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Brief Description of the Drawings
The apparatus of the invention will now be described with reference to the
accompanying drawings, in which:
Figure 1 is perspective view of a prior art breaker plate having transverse
wear and breaker ribs;
Figure 2 is a perspective view of a first embodiment of breaker plate of the
present invention for use on shaker tables;
Figure 3 is a perspective view of a second embodiment of breaker plate of the
invention for use in a rotary breaker; and
Figure 4 is a perspective view of a third embodiment of breaker plate of the
invention for use in a rotary breaker.
Description of the Preferred Embodiments
As has been described in U.S. Patent Application Serial No. 12/153,327, the
hard
facing of steel equipment used in the excavation and transfer of oil sands by
providing dual
layers of a particulate carbide such as tungsten carbide dispersed in a metal
alloy matrix on
a metal substrate, wherein the matrix metal of an inner first layer
metallurgically bonded to
the substrate is softer than the matrix metal of an outer second layer
metallurgicaly bonded
to the inner layer, substantially enhances the wear, abrasion and impact
resistance of the
hard facing.
The metal matrix alloy may be nickel-, cobalt- or iron-based and may comprise,
for
example, a nickel-base matrix alloy for the first and second layers, or a
nickel-base matrix
alloy for the first layer and an iron-base matrix alloy metallurgically-bonded
onto the first
nickel-base matrix alloy. Dual layers of nickel-base alloys have been found
suitable for
rolling, high impact rotary breaker screens whereas a second layer of a less
expensive iron-
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base matrix alloy containing dispersed angular tungsten carbide particles
metallurgically-
bonded onto a nickel-base matrix alloy has been found suitable for sliding,
low impact
screen applications encountered in high volume applications having smaller
impact forces.
The particulate carbide, preferably tungsten carbide, comprises about 55 to 65
wt%
of the coatings, the carbides of the first inner layer preferably being
rounded, i.e. non-
angular, and the carbides of the second outer layer being angular such as
produced from
crushed and sintered friable tungsten carbide.
The inner layer must be softer than the outer layer and we have found that an
inner
layer having a matrix hardness of about 30 - 40 Rc and an outer layer having a
matrix
hardness of about 50 - 60 Re surprisingly provide significantly improved hard
facing to
steel wear surfaces.
The matrix alloy layers containing dispersed carbides of the inner and outer
layers
preferably are deposited in a thickness in the range of 2.5 - 3.5 mm. The
orientation of the
second layer should be deposited in a different orientation than the
orientation of the first
layer, preferably perpendicular to the orientation of the first layer or in
the range of 45 to
90 to the orientation of the first layer.
The hard facing of a metal substrate, typically a steel substrate, is applied
in two
passes, preferably by plasma transferred arc welding. Each pass should be
applied so that
the second pass overlaps and is fused to the first pass, and not in the same
orientation,
preferably at an angle of from about 45 to about 90 to each other. The first
pass involves
welding a mixture comprised, for example, of about 37 to 43 wt% nickel-based
matrix
alloy containing about 3.8 wt% C, 1.2 wt% B, 4.0 wt% Si, 6.7 wt% Cr, 2.1 wt%
Fe and
82.2 wt% Ni and about 63 to 57 wt% dense and non-angular tungsten carbide
particles by
plasma transferred arc welding at a temperature in the range of about 250 -
350 C,
preferably about 290 C, onto a steel substrate at a thickness in the range of
2.5 to 3.5 mm.
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A first inner coat produced by the method of the invention at a temperature of
290 C with nickel-based particles and tungsten carbide particles having a mesh
size of 63
to 180 p had the following representative per cent compositions, with
indicated hardness.
PTA Alloy #1 Matrix Hardness Re 33 - 34
Carbon Boron Silicon Chrome Iron Nickel Tungsten
3.75-3.90 0.5-0.59 1.55 - 1.67 2.8-2.9 0.9-0.99 33.2-34.9 Balance
PTA Alloy #2 Matrix Hardness Re 31 - 32
Carbon Boron Silicon Chrome Iron Nickel Tungsten
3.84-3.96 0.48-0.52 1.60-1.64 2.65-2.82 0.85-0.94 34.1-35.1 Balance
PTC Alloy #3 Matrix Hardness Re 35 - 36
Carbon Boron Silicon Chrome Iron Nickel Tungsten
3.82-3.93 0.52-0.56 1.59-1.67 2.75-2.89 0.92-1.01 33.9-34.8 Balance
The second pass onto the coat of the first pass involves welding a mixture
comprised, for example, of about 37 to 43 wt% nickel-based alloy particles
containing 2.3
wt% C, 3 wt% B, 3 wt% Si, 0.5 wt% Fe and 91.2 wt% Ni and about 63 wt% to 57
wt%
dense and angular friable sintered tungsten carbide particles in a cast and
crushed condition
by plasma transferred arc welding at a temperature in the range of about 300
to 375 C,
preferably about 315 C at a thickness in the range of 2.5 to 3.5 mm.
A second outer coat produced by the method of the invention at a temperature
of
315 C with nickel-based particles and tungsten carbide particles having a mesh
size of 63
to 150 p had the following representative compositions with indicated
hardness.
PTA Alloy #4 Matrix Hardness Re 52 - 54
Carbon Boron Silicon Iron Nickel Tungsten
2.30 - 2.40 1.22 - 1.29 1.18 - 1.29 0.17 - 0.24 37.05 - 37.44 Balance
PTA Alloy #5 Matrix Hardness Re 55 - 58
Carbon Boron Silicon Iron Nickel Tungstei__~
2.37 - 2.42 1.18 - 1.25 1.21 -1.29 0.20 - 0.28 37.38 - 37.52 Balance
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PTA Alloy #6 Matrix Hardness Re 54 - 56
Carbon Boron Silicon Iron Nickel Tungsten
2.34 - 2.44 1.15 - 1.23 1.20 - 1.30 0.22 - 0.29 37.44 - 37.62 Balance
A first pass of nickel-based matrix alloy comprised of about 37 to 48 wt%
nickel-
based matrix alloy described above had a second pass of iron-based matrix
alloy having
about 60 wt% crushed and sintered tungsten carbide particles deposited onto
the first inner
coat of nickel-based alloy at a temperature of about 315 C. The second outer
coat had the
following general per cent composition.
Alloy #4 Matrix Hardness Re 56 to 59
Carbon Boron Silicon Iron Nickel
0% 3% 3% 48% Balance
This combination of softer inner layer of nickel-based matrix alloy containing
carbides having a hardness in the range of Re 31 - 36 and outer layer of
harder iron-based
matrix alloy containing carbides having a hardness in the range of Re 56 - 59
was effective
in extending the life of hard faced screens in shaker box applications for a
three-fold
reduction of down time and in rotary breaker applications for a two-fold
reduction of down
time compared to conventional screens.
We have found that the provision of shaped stud-like protrusions on the
wearing
surface of the breaker plates significantly enhances the rate of breaking down
large
oversized lumps of oil sands passing over inclined shaking tables or through
rotary drums
having an axis of rotation inclined at an angle of about 10 to the
horizontal.
With reference first to Figure 1 of the drawings, a prior art breaker plate 10
is
shown made of carbon steel having transverse rows of openings 12 forming a
sieve for the
passage of undersize particles of oil sand therethrough. Transverse bars 14 of
white cast
iron typically are welded onto the substrate of carbon steel plate 10 between
the transverse
rows of openings 12 to assist in breaking down the lumps of oversize oil sands
passing
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over. Not only is the process of breaking down the lumps not efficient, but
also the bars
are brittle due to the welding process required to attach the bars to the
substrate and
therefore subject to cracking by the impact thereon of heavy lumps of oil
sands.
With reference now to Figure 2 of the drawings, carbon steel plate 20 having
transverse rows of holes 22 found therein has transverse rows of upstanding
wedge-shaped
protrusions or studs 24 attached to plate 20 between the transverse rows of
holes 22 and
comprising at least 10% of the area of the plate. Protrusions 24 are formed on
or attached
to plates 20 by welding. The apex or point 28 of the wedge shaped protrusions
faces the
oncoming travel of oversize lumps and the wedges are short and wide to
effectively absorb
the impact of oil sand lumps dropped thereon and to break down the lumps. This
embodiment is particularly suited for use on shaker tables.
Figures 3 and 4 show breaker plates 40, 42 particularly suited for use in
rotary
breaker drums and have an arcuate shape to fit the peripheral contour of the
drums.
Typical drums employed in the oil sands are 7 feet or 16 feet in diameter
having
rectangular breaker plates 34 x 45 inches in size or 72 inches square
respectively. With
reference to Figure 3, breaker plate 40 has transverse rows of openings 44
with transverse
rows of pyramid protrusions 46 arranged between the rows of holes 44.
Protrusions 46 are
formed on an elongated steel strip 48 which is welded to the breaker plate 40
whereby the
pyramid protrusions 46 preferably are aligned with the longitudinal plate
metal 50 between
holes 44 with spaces 52 between the protrusions 46 aligned with the holes to
facilitate
passage of undersized material through the holes. Each pyramid protrusion has
a square
base and preferably a flattened apex.
With reference to Figure 4, breaker plate 42 has transverse rows of holes 54
with
transverse rows of pyramid protrusions 56 arranged between the rows of holes
54.
Pyramid protrusions 56 are formed on an elongated steel strip 58 and have an
elongated
rectangular bases extending along the steel strip whereby the sides of the
pyramid
protrusions abut each other. The rows of protrusions 56 extend from one side
wall 60 to
the opposite side wall 62 and are welded to the breaker plate whereby the
apices 64 of one
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row of protrusions 56 alternate with the valley 66 of the adjacent rows such
that one row of
apices are aligned with holes 54 and the next row of apices are out of
alignment with the
holes 54.
The exposed surfaces of each pyramid or wedge protrusion preferably has a dual
layer hard faced coating, as has been described above, or is formed of a wear
and erosion
resistant material..
The present invention provides a number of important advantages. Oversized
lumps from crushed oil sands processed by primary roll crushers are
effectively
disintegrated and broken down in size suitable for wet screening with hot
water for
slurrying and pumping as a slurry or separation of bitumen from the sand. The
breaker
plates having the hard-faced shaped protrusions on wearing surfaces thereof or
fabricated
of wear and erosion resistant material covering at least 10% of the area of
the plate surface
provide point load impact zones to the lumps impacting thereon to quickly
break down the
oil sands to a sieve size that will pass through the plate holes, thereby
minimizing impact
loading and abrasive wear on the breaker plates and extending the working life
of the
breaker plate components.
It will be understood that other embodiments and examples of the invention
will be
readily apparent to a person skilled in the art, the scope and purview of the
invention being
identified in the appended claims.
